Fix OpenAPI operation name plural appropriately

requirements/requirements-optionals.txt

@@ -3,6 +3,7 @@ coreapi==2.3.1
 coreschema==0.0.4
 django-filter>=2.4.0,<3.0
 django-guardian>=2.4.0,<2.5
+inflection==0.5.1
 markdown==3.3;python_version>="3.6"
 markdown==3.2.2;python_version=="3.5"
 psycopg2-binary>=2.8.5,<2.9

rest_framework/schemas/openapi.py

@@ -11,6 +11,7 @@ from django.core.validators import (
 )
 from django.db import models
 from django.utils.encoding import force_str
+from inflection import pluralize
 
 from rest_framework import (
     RemovedInDRF314Warning, exceptions, renderers, serializers
@@ -247,8 +248,8 @@ class AutoSchema(ViewInspector):
             if name.endswith(action.title()):  # ListView, UpdateAPIView, ThingDelete ...
                 name = name[:-len(action)]
 
-        if action == 'list' and not name.endswith('s'):  # listThings instead of listThing
-            name += 's'
+        if action == 'list':
+            name = pluralize(name)
 
         return name
 

tests/schemas/test_openapi.py

@@ -695,6 +695,21 @@ class TestOperationIntrospection(TestCase):
         operationId = inspector.get_operation_id(path, method)
         assert operationId == 'listUlysses'
 
+    def test_operation_id_plural(self):
+        path = '/'
+        method = 'GET'
+
+        view = create_view(
+            views.ExampleGenericAPIView,
+            method,
+            create_request(path),
+        )
+        inspector = AutoSchema(operation_id_base='City')
+        inspector.view = view
+
+        operationId = inspector.get_operation_id(path, method)
+        assert operationId == 'listCities'
+
     def test_operation_id_override_get(self):
         class CustomSchema(AutoSchema):
             def get_operation_id(self, path, method):